1. Field of the Invention:
The present invention relates to an optical disk head used in an optical recording apparatus, and a method for producing the same. More particularly, the present invention relates to an optical disk head which is thin and lightweight, and achieves easy mechanical alignment of components, and a method for mass-producing such optical disk heads.
2. Description of the Prior Art:
An optical recording apparatus includes an optical disk head so as to read signals recorded in an optical recording medium such as compact disks (CD), optical disks, and optical card memories. The optical head is necessarily equipped with a servocontrol such as a focus servo or a track servo.
There is a typical optical disk head known in the industry illustrated in "Autofocus Hitec Technologies" (edited by M. Kohno, published by Keiei System Kenkyusha) which will be described by reference to FIG. 1:
A light source 1 radiates a laser beam 17 which is made parallel by a collimator lens 18 and caused to pass through a beam splitter 19. Then it is focused on an optical disk 7 by an objective lens 20. The laser beam is reflected from the optical disk 7, and is made parallel by the objective lens 20. After being reflected from a boundary face 19' of the beam splitter 19, is introduced into a focus-track error detector optics 21 which includes a convex lens and a cylindrical lens. Thus, a reproducing signal, a focus-error signal and a track-error signal are read.
The known optical disk head shown in FIG. 1 has disadvantages in that the optical system becomes complex and the mechanical alignment of optical components requires high precision. Thus, the resulting optical head is likely to become large, heavy and costly.
In order to solve these problems, efforts are being made to develop optical integrated circuits including a substrate in which a waveguide and various optical components are provided. However, a difficulty arises from the fact that light beam is propagated throughout the waveguide as a wave having a crest-type distribution of light intensity, thereby requiring the light beam to be treated under the theory of wave optics. This means that the efficiencies at which a light beam is introduced into the waveguide and output therefrom are likely to reduce, and the optical information propagated through the waveguide is one-dimensional.
Japanese Laid-Open Patent Publications Nos. 2-301702, 2-301703 and 2-301704 disclose planar reflection optical devices. These devices employ a transparent substrate with reflective lenses so that a light beam is allowed to propagate in a zigzag form through the substrate but they have no optical pickup means for catching a light beam reflected from an optical recording medium. As a result, these devices cannot be used for an optical disk head.